Motor pump aggregate

ABSTRACT

A motor pump aggregate M has a housing  1  defining an oil reservoir with first and second chambers R 1 , R 2 . An electromotor  2  is driving via its motor shaft W at least one radial piston pump arrangement P 1  provided within said first chamber R 2 . Both chambers R 1 , R 2  are separated by a separation wall  7 . A filling and pressure biasing system V is provided for said first chamber R 1  in order to adjust within said first chamber R 1  a predetermined oil filling level and a pre-selected oil pressure pre-biasing for said radial piston pump arrangement P 1.

DESCRIPTION

[0001] The present invention relates to a motor pump aggregate accordingto the preamble part of claim 1.

[0002] In the motor pump aggregate as known from DE 299 06 881 U oilreturning from the hydraulic system either directly flows into the firstchamber or finally flows into the first chamber from the second chambervia a lower open passage in the separation wall. In a horizontaloperation position of the motor pump aggregate the same filling level isachieved in both chambers. A ventilation bore situated in an upperportion of the separation wall allows air to pass through. Saidventilation bore has a significantly smaller cross-section than thepassage in said separation wall. The radial piston pump arrangementprovided within said first chamber has to generate extremely highhydraulic pressures with small supply rate, e.g. between 700 bars and800 bars. After longer resting periods of the motor pump aggregate orwhen tilting or moving the motor pump aggregate air can be trapped inthe oil. The intrusion of trapped air even cannot be avoided reliably byusing downwardly extending suction tubes for the radial piston pumpelements. As the pistons of the radial piston pump elements are madewith small diameters any trapped air leads to a significant decrease ofthe supply efficiency of the radial piston pump arrangement such thatthe desired maximum pressure cannot be reached any more.

[0003] Further publications relating to motor pump aggregates are GB 2000 221 A, DE 295 19 941A, DE 393 16 99A, EP 08 90 741A, and DE 38 39 689A.

[0004] It is an object of the invention to provide such a motor pumpaggregate with increased supply efficiency allowing to reliably reachthe needed maximum pressure under all operating conditions.

[0005] Said object can be achieved by the features of claim 1.

[0006] By means of the filling and pressure pre-biasing systemassociated to the first chamber for all operating conditions not onlythe predetermined filling level is reliably maintained in said firstchamber but also even a hydraulic biasing pressure is generated at thesuction side of the radial piston pump arrangement. Said measuressignificantly increase the supply efficiency of the radial piston pumparrangement and avoids air getting trapped in the radial piston pumpelements. Said hydraulic pre-biasing pressure even allows the smalldiameter pump elements to automatically remove occasionally trapped air.Due to the increased supply efficiency extremely high pressures of e.g.700 bars to 800 bars reliably can be reached by radial piston pumpelements having small pistons and operating with small supply rates. Theaggregate predominantly is developed for operation with horizontal motorshaft (lying working position). However, the concept of the pressurepre-biasing is of advantage also for aggregates operating in uprightposition.

[0007] A spring loaded pre-biasing valve allows an oil exchange from thefirst chamber into the second chamber via the exchange flow channel onlyfirst then when the adjusted pre-biasing pressure is reached within thefirst chamber. Air present within the first chamber is transferred viathe ventilation channel into the second chamber. The filling levelwithin the first chamber at least is raised up to the height position ofthe ventilation channel. Oil returning from the return system into thefirst chamber is under a certain return pressure from which thepre-biasing valve derives the intended pre-biasing pressure for thefirst chamber. The return oil volume furthermore presses residual airfrom the first chamber via the ventilation channel into the secondchamber. Even after a longer resting period of the motor pump aggregateand/or in case of movements of the aggregate during transport and/or incase of preliminary strong oil supply demand no air is allowed toentered the radial piston pump arrangement. In case that neverthelessair should be trapped for other reasons the radial piston pump elementseven are able to automatically remove trapped air more easily thanks tothe pre-biasing pressure within said first chamber. Alternatively oradditively the needed pre-biasing pressure and the predetermined fillinglevel also can be achieved by means of a charging pump.

[0008] A pre-biasing valve having the form of a screw-in check valvewithin said separation wall is easy to manufacture and to mount.Screw-in check valves are available for fair costs, only need littlemounting space, and are very reliable in function.

[0009] Compact dimensions, a stable heat household even for permanentoperation and manufacturing the motor pump aggregates for fair costs arepossible if the stator winding section of the electromotor designed asan oil immersed motor directly is shrunk into the light metal profilesection forming a part of the housing or the oil reservoir,respectively.

[0010] At least a flattened section in the periphery of the statorwinding part is forming an oil exchange passage through which oil forexample can be brought to a motor shaft bearing situated remote from theradial piston pump arrangement. Except in the region of the region ofthe at least one peripheral flattened part a direct metallic contact isachieved between the stator winding part and the light metal profilesection. By said direct metallic contact heat from the stator windingpart is conveyed to the outer side without an insulating oil filmbetween the stator winding part and the light metal profile section. Theheat conveyed outwardly then is radiated off by a rib structure and/oris removed with the help of a fan.

[0011] The ventilation channel ought to be provided higher up than thesuction areas, particularly the suction area located high up, of theseveral radial piston pump elements distributed around the pump shaft.Said ventilation channel ought to be located very close to the upperboundary of the first chamber. The oil exchange channel, to thecontrary, can be located at the height position of the motor or pumpshaft.

[0012] A significant improvement of the supply sufficiency already canbe achieved by a relatively moderate pre-biasing pressure of about 0.1bar within the first chamber. Expediently said pre-biasing pressure isgenerated by means of the returning oil having the return systempressure. However, alternatively or additively said pre-biasing pressurecan be generated by means of a charging pump.

[0013] A charging pump expediently is driven from the same motor shaftas the other pump sections and is received within the first or secondchamber.

[0014] Radial piston pump elements having piston diameters between 4 mmand 9 mm are employed to achieve the needed maximum pressure. In thiscase maximum pressures from about 700 bars to 800 bars can be reached byrelatively low driving power. A moderate driving power namely isexpedient in view to the start-up current of the electromotor in orderto allow to connect the motor pump aggregate as a portable unit to thenormal electric net without overloading the usual relatively weak fusesusually provided. The motor pump aggregate expediently is a portableunit with a weight less than about 25 kilos.

[0015] In order to simplify the first filling of the first chamber andin order to allow to easily remove the oil a further passage containinga check valve is provided in said separation wall. Said check valveblocks in flow direction from the first chamber to the second chamberand opens with relatively low resistance in the opposite flow direction.An oil outlet to a removal screw can be connected to said removalpassage, such that the first chamber can be filled when filling thesecond chamber.

[0016] Structurally simple the seat of the check valve directly isformed within said removal passage. A closure ball is co-operating withsaid seat. Said closure ball is secured by means of a securing ringagainst being lost. Expediently even in the second chamber an oilremoval screw can be provided.

[0017] Embodiments of the invention will be explained with the help ofthe drawings. In the drawings is:

[0018]FIG. 1 a longitudinal section of a motor pump aggregate,

[0019]FIG. 2 a cross-sectional view of the motor pump aggregate of FIG.1 in sectional plane A-A in FIG. 1,

[0020]FIG. 3 a cross-sectional view of the motor pump aggregate insectional plane B-B in FIG. 1,

[0021]FIG. 4 a cross-sectional view of the motor pump aggregate insectional plane D-D in FIG. 1,

[0022]FIG. 5 a more detailed longitudinal sectional view in sectionalplane C-C in FIG. 2, and

[0023]FIG. 6 a schematic block circuit of the motor pump aggregate withmounted control valve block and a connected to hydro-consumer, whereinwithin said block circuit in dotted lines an alternative or additivevariation is indicated.

[0024] A motor pump aggregate M in FIG. 1 e.g. is a portable unit havinga weight below about 25 kilos and is intended for a lying operationposition. Said motor pump aggregate, however, does not need to benecessarily a portable unit. Furthermore, it can be developed for anupright operation position.

[0025] In a housing 1 confining an oil reservoir an electromotor 2 issituated. Said electromotor 2 is designed as an oil immersible motor andserves as a drive for a radial piston pump arrangement P1 (high pressurestage) and a low pressure stage P2 e.g. defined by a gearwheel pump 12.A motor shaft W is situated essentially horizontally. Housing 1 includesa light metal profile section 3 (rib tube) with cylindrical inner wall.A stator winding part 4 of electromotor 2 directly is shrunk into saidlight metal profile section 3. A rotor 5 is centred within statorwinding part 4 on motor shaft W. Motor shaft W is supported in bearingsin an end cap 6 and a separation wall 7 of said housing 1. A furtherhousing part 8 is fixed to separation wall 7. Separation wall 7 isseparating a first chamber R1 of said oil reservoir from a secondchamber R2. Pump stage P2 is secured to separation wall 7 within secondchamber R2. Said stator winding part 4 is separating the first chamber Rfrom a further chamber R′. Motor shaft W extends through said furtherchamber R1′ and through a bearing located within said end cap 6 towardsan exteriorly positioned fan wheel 9. For example, by means of anexcenter 10, motor shaft W is driving several radial piston pumpelements 11 which are distributed around said motor shaft W within saidradial piston pump arrangement P1. There are e.g. four radial pistonpump elements 11 which are secured to said separation wall 7. The term“radial piston pump element” has the meaning that each pump elementcontains a linearly reciprocable piston driven in radial directionlooking on the axis of motor shaft W. Motor shaft W further is drivingsaid gear wheel pump 12. The pump arrangements P1, P2 e.g. are connectedinside separation wall 7 with a control valve block 13 which e.g. ismounted to the exterior side of housing 1. A return channel 14 connectedto-a return system R extends within separation wall 7 towards said firstchamber R1. In an upper portion of separation wall 7 a ventilationchannel 15 interconnects both chambers R1, R2.

[0026] In a lower portion of separation wall 7 a removal channel 16 isprovided, e.g. in the form of a bore extending obliquely downwardly fromfirst chamber R1 into second chamber R2. Within said removal channel 16a valve seat 17 is provided, e.g. integrally formed, onto which a ballclosure member 18 can be seated. Valve seat 17 and ball closure member18 define a check valve blocking in flow direction towards said secondchamber R2 and opening in case of a weak pressure difference into theopposite flow direction towards the first chamber R1. Said ball closuremember 18 is secured by means of a securing ring 19 against falling out,e.g. by means of a Seeger ring. A drain 20 extends via sidewards locatedpockets from removal channel 16 to a lower removal screw 21.

[0027] Also in housing part 8 a lower removal screw 22 can be provided.A filling and pressure pre-biasing system V is provided for the firstchamber R1. Said system comprises in FIGS. 2, 3 and 4 a pre-biasingvalve F situated within said separation wall 7, furthermore, e.g. thereturn channel 14 connected to the return system R, and said ventilationchannel 15. Said filling and pressure biasing system V serves togenerate a predetermined filling level and a selected hydraulicpre-biasing pressure within said first chamber R1 in operation of saidmotor pump aggregate, in order to improve the supply efficiency of saidaggregate.

[0028] In FIGS. 2 and 3 said pre-biasing valve F is locatedsubstantially at the height position of said motor shaft W. FIG. 2 showsa filling device 23 for said second chamber R2. In FIG. 3 saidpre-biasing valve F is located within an exchange channel 30 inseparation wall 7. The radial piston pump arrangement P1 consists offour radial piston pump elements 11, each of which has a piston 25, ahousing 26 and a suction side 27. The pressure sides of elements 11 areconnected via a channel system 28 in separation wall 7 to control valveblock 13. Pistons 25, e.g. are made with a diameter between 4 mm and 9mm. Return channel 14 in separation wall 7 leads from said return systemR into said first chamber R1.

[0029] In FIG. 4 the stator winding part 4 directly is shrunk into saidlight metal profile section 3 such that flattened portions 29 at theperiphery of said stator winding part 4 are defining oil passages tosaid further chamber R1′ and to a bearing of motor shaft W situated atthe right side in FIG. 1. In this way a dominant part of thecircumference of stator winding part 4 is contacting without an oil filmin-between the cylindrical inner wall of said profile section 3, whichis formed with exterior longitudinal ribs 24.

[0030] Said pre-biasing valve F (FIG. 5) e.g. is inserted from thesecond chamber R into the exchange channel 30. In a stepped bore havinga terminal inner thread section a valve seat insert 31 is seated, whichis positioned by means of a screwed-in closure spring-retainer 33 and isconnecting with a closure element 32 preferably having a sphericalsealing surface. Said closure element 32 is loaded by a pre-loadingspring 34 in closing direction (screw-in check valve).

[0031] In block circuitry in FIG. 6 said pre-biasing valve F and saidcheck valve 17, 8 in separation wall 7 are blocking in mutually oppositeflow directions. Said ventilation channel 15 forms a throttledconnection between said first and second chambers R1, R2. The returnsystem R of the hydraulic system S is connected to return channel 14.Control components of said hydraulic system S may be received withincontrol valve block 13. A multiple ways control valve can be connectedto said control valve block 13 as well as a connection towards ahydraulic consumer Z. Within return system R at least during operation apredetermined return system pressure is active. Oil returning intoreturn channel 14 and said return system pressure are used to producewithin said first chamber R1 a filling level up to at least the heightposition of ventilation channel 15 and to generate a pre-selectedpre-biasing pressure, respectively, which is controlled by saidpre-biasing valve F. Oil is passing from said first chamber R into saidsecond chamber R2 as soon as the pressure within said first chamber Rtends to exceed said predetermined or selected pre-biasing pressure.Said pre-biasing pressure e.g. is adjusted to 0.1 bar.

[0032] As an alternative solution a charging pump P3 is indicated indotted lines either in the first or the second chamber R1, R2. Saidcharging pump P3 is supplying said first chamber R1 with oil in order togenerate the filling level and pre-biasing pressure. Instead an externalcharging pump or another charging pressure source could be used for thispurpose.

1. Motor pump aggregate (M) comprising a housing (1) defining an oilreservoir by first and second chambers (R1, R2), an electromotor (2)within said housing (1) driving by its motor shaft (W) at least a radialpiston pump arrangement (P1) provided within said first chamber (R1),and a separation wall (7) between said first and second chambers (R1,R2) characterised in that a filling and pressure biasing system (V) isprovided for said first chamber (R1) for establishing within said firstchamber (R1) a predetermined oil filling level and a pre-selectedpre-biasing oil pressure for said radial piston pump arrangement (P1).2. Motor pump aggregate as in claim 1 , characterised in that said firstchamber (R1) is loaded by the return pressure of a return system (R)connected to said motor pump aggregate (M) and/or by a charging pressureof a charging pump (P3), and that a spring loaded pre-biasing valve (F)and an open ventilation channel (15) are provided preferablyrespectively within in said separation wall (7), said pre-biasing valve(F) being situated within an exchange channel (30) extending betweenboth chambers (R1, R2), said pre-biasing valve blocking flow in flowdirection from said second chamber into said first chamber (R1), saidopen ventilation channel (15) being situated above said exchange channel(30).
 3. Motor pump aggregate as in claim 2 , characterised in that saidpre-biasing valve (F) is designed as a screw-in check valve and includesa valve seat insert (31), a screw-in spring retainer (33), a pre-loadingspring (34) and a closure element (32) having a spherical sealingsurface.
 4. Motor pump aggregate as in claim 1 , characterised in thatsaid housing (1) includes a light metal profile section (3) withcylindrical inner wall and outer ribs, that a stator winding part (4) ofsaid electromotor (2) directly is shrunk into said light metal profilesection (3), said electromotor (2) being made as an oil immersed motorwith lying motor shaft (W), and that said stator winding part (4) has atleast one peripheral flattened portion (29) defining with saidcylindrical inner wall of said section (3) an oil exchange passage. 5.Motor pump aggregate as in claim 2 , characterised in that said radialpiston pump arrangement (P1) comprises several radial piston pumpelements (11) secured to said separation wall (7) and distributed aroundsaid motor shaft (W), and that in an operation position of said motorpump aggregate (M) said ventilation channel (15) is provided above thesuction ranges (27) of said radial piston pump elements (11) and saidexchange channel (30) is located essentially at the height position ofsaid motor shaft (W).
 6. Motor pump aggregate as in claim 2 ,characterised in that said pre-biasing pressure within said firstchamber (R1) is derived from the return pressure of a hydraulic circuitconnected to the motor pump aggregate and amounts e.g. to about 0.1 bar.7. Motor pump aggregate as in claim 2 , characterised in that withinsaid second chamber (R2) at said separation wall (7) a low pressure gearwheel pump arrangement (P2) is provided.
 8. Motor pump aggregate as inclaim 1 , characterised in that said first chamber (R1) is connected toa charging pump (P3), e.g. to a charging pump (P3) situated within saidfirst or second chamber (R1, R2) and driven by said motor shaft (W). 9.Motor pump aggregate as in claim 1 , characterised in that said radialpiston pump elements (11) are equipped with pistons (25) of a diameterbetween about 4 mm to about 9 mm, and that the maximum supply pressureto be reached by said radial piston pump elements (11) is set to about700 bars to 800 bars.
 10. Motor pump aggregate as in claim 1 ,characterised in that said motor pump aggregate (M) is a portable unithaving a weight less than about 25 kilograms.
 11. Motor pump aggregateas in claim 2 , characterised in that a removal channel (16) is providedwithin said separation wall (7), said removal channel (16) extending inoperation position of said motor pump aggregate (M) from said firstchamber (R1) obliquely downwards into said second chamber (R2), that acheck valve is contained within said removal channel (16), said checkvalve blocking in flow direction from said first chamber (R1) into saidsecond chamber (R2), and that a drain (20) is leading from said removalchannel (16) to a lower positioned removal screw (21).
 12. Motor pumpaggregate as in claim 11 , characterised in that said check valveconsists of a ball closure member (18) and a valve seat (17) formed intosaid removal channel (16), and that said ball closure member (18) issecured within said removal channel (16) by a securing ring (19), e.g. aSeeger ring.